Many methods for controlling the driving behavior of a vehicle are known in the art which use tire sensors for sensing the forces and moments that act on the tires. The term ‘tire sensor (SWT sensor)’ in this context refers to the encoder mounted in or on the tire and at least one pick-up for measuring data that is associated with the encoder and mounted on the chassis in a stationary manner. Whereas in EP 0 444 109 B1 the deformation of the tire profile area of the tire, i.e., the tire print, is monitored, WO 96/10505 proposes detecting the deformation of the side wall of a tire, i.e., torsion deformations, by measuring a period of time that elapses between the passing of at least two markings arranged on the rotating wheel at a different radius relative to the axis of rotation. WO 97/44673 describes a tire sensor which detects a variation of the phase position and/or the amplitude between output signals sent by pick-ups for measuring data when the tire is deformed due to forces acting on the tire. The size of the air slot between the encoder or the magnetic areas embedded into the tire side wall and the e.g. active, magnetoresistive pick-ups for measuring data produce the signal which is used for the allocation of the lateral or transverse forces that act upon the tire. Consequently, the variations of the signals established by the pick-up for measuring data reproduce the deformations or variations of the tire side wall which are caused by the transverse forces that act on the wheels, while the change in the phase position between the two pick-ups for measuring data which are arranged on an outside and an inside radius relative to the axis of rotation of the wheel define a signal for the calculation of the longitudinal forces.
Another air tire equipped with a magnetic encoder is described in DE 196 20 582 A1 to which reference is made in full extent. The forces that act on a wheel having a tire of this type are reproduced in the way of signals correlated to forces in the pick-ups for measuring data or signal conditioning devices and used in motor vehicle control systems to regulate or control vehicles, especially for proportioning and/or modulating the brake pressure in the wheel brakes of the wheels.
When determining the functional correlation between the amplitude and/or phase signal and the forces that act on the wheels or the tires, measuring wheel rims are used as described, for example, in EP 0 352 788 A2. It is necessary in this context to arrange the pick-ups on the vehicle body or the wheel suspension so as to duplicate them in order to make the signals reproducible that are responsive to the air slot. Tolerances which occur in the arrangement or manufacture of the pick-ups for measuring data, and/or different wheel rim systems, e.g. with different rim offsets, cause discrepancies in determining the forces that act on the wheels or tires.